I'm using tumbleweed and would like to install virtualbox, however it
depends on virtualbox-host-kmp-desktop version
4.0.4_k2.6.37.1_1.2-1.6.1 which in turn depends on kernel-desktop-base
version 2.6.37.6-0.5.1. However tumbleweed has kernel-desktop version
2.6.39.3-37.1 which means I'd need to downgrade my kernel to use
virtualbox. Could tumbleweed provide a version of virtualbox for the
newer kernels?

I'm using this kernel:
kernel-desktop-2.6.39.3-37.1.x86_64

I'm using this VirtualBox:
VirtualBox-4.0-4.0.12_72916_openSUSE114-1.x86_64